Off-flavor Management

1. Off-flavor Management Gary Burtle Animal & Dairy Science University of Georgia

2. Off-flavor Problem Linked primarily to Oscillatoria. Microcystis and Anabaena May also be linked to Aphanizomenon 1,289,000 pounds of fish affected in August 2000 Copper sulfate cannot be utilized in all ponds

3. Approach Modify chemical, physical, or biological environments to discourage blue-green algal growth Utilize herbicides to control blue-green algae Utilize plankton eating fish to control algal populations

4. Commonly Used Treatments Copper sulfate Copper liquid formulations Diuron Shad stocked to eat algae

5. Copper Algicides Only algicides registered for legal use Not consistent in control of problem algae Not selective to problem algae Little margin of safety to fish Can only be used with alkalinity above 50 ppm 0.1 ppm to 0.25 ppm may control for a short time

6. Copper Liquid Formulations Use label recommendations Some can be used at low alkalinities Chelates and EarthTech Effects do not last very long

7. Shad Stocking 1,000 per surface acre Stock early in the Spring or in late Winter May delay the dominance of Blue-greens until August or later May shift algal populations toward a diverse community of 20 or more species

8. Plankton Feeding Fish Shad select for phytoplankton Fathead minnows are omnivorous but consume algae U. Georgia, Auburn U., Louisiana State U. are involved in this regional project

9. Fish Stocking Densities Shad of about 1,000 per acre should produce about 200 to 400 pounds per acre Stock shad in early spring to allow spawn Fathead minnows at 2,000 per acre, use spawning structure Catfish at 7,500 to 10,000 per acre

10. Shad Results - Bluegreen Numbers (x 1,000,000/L)

11. Catfish Only - Bluegreen Numbers (x 1,000,000/L)

12. Minnows Stocking- Bluegreen Numbers (x1,000,000/L)

13. Algal Control Evidence Shad ponds have smaller numbers of Blue-greens and fewer off-flavor species Ponds were also stocked with 7,000 catfish per acre and fed up to 160 lb/A/day Algal scums were visible in some shad ponds Off-flavor was absent in ponds with shad

14. Industry Trends Copper use will continue, sometimes rotated with Diuron Diuron rate now about 1/2 oz per surface acre down from 1/2 oz per acre-ft Shad will be stocked where they are available Off-flavor still occurs, but with lower frequency

15. Label Extension Proceedure Collect data to justify need for label extension Complete Section-18 application Obtain clearance for submission by GA Department of Agriculture Obtain permission for extension by Griffin Corp. GA Dept Ag applies to US EPA

16. Algae Species in Off Flavor Ponds